In orthodontics, one type of malocclusion is encountered in which an anterior openbite is caused by occlusal contacts only occurring posteriorly. The standard method to correct this kind of malocclusion is with surgical intervention whereby a wedge of bone is removed from the maxilla apical to the maxillary root tips. After removal of the wedge of bone, autorotation of the mandible will occur thereby correcting the anterior openbite. It is the intent of this invention to eliminate this surgical procedure and provide a device which selectively intrudes the posterior teeth of both the maxilla and mandible and thereby facilitates the closure of anterior openbite malocclusions by autorotation.
Umemori et al, (Am J Orthod Dentofacial Orthop, 115:166, 1999), in 1999, first described a bone anchor system to intrude posterior teeth and facilitate correction of an anterior openbite without surgery. Several years later, Sherwood, in 2002, (Sherwood, K H et al., Am J Orthod Dentofacial Orthop, 122:593, 2002) and 2003, (Sherwood, KH et al., (Angle Orthod, 73:597, 2003), described similar mechanisms to facilitate anterior rotation and closure of an anterior openbite. Additional descriptions of similar approaches were described by Erverdi, (Erverdi, N et al., World J. Orthod, 3:147, 2002) in 2002 and by Miyawaki, S et al., (Am J Orthod Dentofacial Orthop, 124:84, 2002) in 2003. An overall review of orthodontic anchorage in general, including specific references to bone plates, was completed by Favero, (Favero, L et al., Am J Orthod Dentofacial Orthop 122:84, 2002) in 2002.
In all of these systems, the bone plate has an extension into the vestibule from which materials or springs are attached to facilitate intrusion of the posterior teeth. The disadvantage to all of the previous methods is that the point of force application cannot be changed during treatment nor can the bone anchor be modified or adjusted prior to insertion or during treatment. A change in the location of force application to the dentition is often required and without a corresponding change on the anchor a different and generally undesirable change in the vector of this force occurs. This change in vector can limit the extent of correction of anterior openbites. If the centroid of the maxillary arch varies from the point of force application, a moment occurs and the resultant rotation around the centroid could actually open the bite thus making the malocclusion worse.
In practice, the surgeon often encounters difficulty in placing the bone plate as distally as desired. Additionally, the clinician attaching the elastomeric materials or springs from the bone plate to the dentition experiences difficulty when the bone plates are placed too far posteriorly. Often, the surgeon has difficulty placing the anchors in the correct location to achieve the desired point of emergence of the bone plate into the vestibule. This variation in height and location of the bone plate for subsequent tooth movement presents significant difficulties to the clinician attempting to intrude the posterior teeth.
An adjustable and/or removable cap on the bone plate permits the surgeon to place the bone plate in a more accessible region of the mouth while extensions from the cap can be used to move the point of force application to the dentition in the most desirable location, i.e., the centroid. By utilizing different configurations for the cap, the point of emergence of the bone plate from the vestibule becomes less critical thus facilitating a more clinically acceptable method of intruding the posterior teeth.